For instance, a tread rubber which is one of rubber members of a vehicle tire is usually formed from a shaped rubber body made up of different rubber compounds so as to have a plurality of rubber sections in a cross-section of the shaped rubber body in order to improve tire performance.
FIG. 7(A) shows a shaped rubber body K1 for a tread rubber having the radially outermost rubber section Ya (so-called cap rubber layer) of a rubber compound Ga which is excellent in abrasion resistance, and a radially inner rubber-section Yb (so-called base rubber layer) of a high-modulus rubber compound Gb.
FIG. 7(B) shows another shaped rubber body K2 for a tread rubber having the above-mentioned rubber sections Ya and Yb and further rubber sections Yc and Yd (so-called wing rubber) of a rubber compound Gc which is excellent in adhesion strength, disposed on both sides of the sections Ya and Yb.
Such a shaped rubber body (K1, K2) having a plurality of rubber sections can be formed by using a rubber extruding machine comprising multiple rubber extruders for different rubber compounds connected to a single extrusion head. See Patent Documents 1 and 2.    Patent Document 1: Japanese Patent Application Publication No. 2002-86540    Patent Document 2: Japanese Patent Application Publication No. 2005-349597
on the other hand, when a shaped rubber body is formed by being extruded from such rubber extruding machine, there is a possibility that gas (air) is trapped between the rubber sections (layers) and remained as voids in the shaped rubber body.
Japanese Patent No. 4863392 discloses a rubber extruder whose cylinder is provided with a degassing device.
If this rubber extruder is used in the above-mentioned rubber extruding machine comprising multiple rubber extruders, it may be possible to remove air or gas in the rubber extruded from each rubber extruder.
However, when the extruded rubbers are merged by passing through an extrusion head (die), there is still the possibility that gas or air is trapped between the rubber sections.